Van Dyke’s CBS series, “Diagnosis Murder” – in which he plays a crusading, investigative doctor – has been airing since 1993 and also stars his son, Barry Van Dyke.

Van Dyke, who worked for years on a one-year contract, said he will retire after this season.

Van Dyke, who turns 75 in December, alluded to former “Tonight Show” host Johnny Carson in making his retirement announcement in Washington.

“I’m going to follow his lead,” Van Dyke said of Carson, who has been almost hermit-like since his retirement in 1992.

CBS, with shows like “Survivor” and “C.S.I.,” has steadily been attracting the younger audience coveted by advertisers – and surprised many in the industry when it decided to renew “Murder” for the 2000-2001 season.

Van Dyke, guesting Sept. 22 on “Larry King Live,” said that he thought “Diagnosis Murder” was “being thrown to the wolves” by CBS because it was scheduled this season opposite “ER.” CBS officials had no comment.